Distribution of Genes and Microbial Taxa Related to Soil Phosphorus Cycling across Soil Depths in Subtropical Forests

Although many studies have focused on the roles of soil microbes in phosphorus (P) cycling, little is known about the distribution of microbial P cycling genes across soil depths. In this study, metagenomic sequencing was adopted to examine the differences in the abundance of genes and microbial taxa associated with soil P cycling between organic and mineral soil in subtropical forests. The total relative abundance of inorganic P solubilizing genes was the highest, that of P starvation response regulating genes was second, and organic P mineralizing genes was the lowest. The soil organic carbon concentration, N:P ratio, and available P concentration were higher in the organic soil than the mineral soil, resulting in abundances of organic P mineralizing genes (appA and 3-phytase), and inorganic P cycling genes (ppa), whereas those of the inorganic P cycling genes (gcd and pqqC) and the P starvation response regulating gene (phoR) were higher in mineral soil. The four bacteria phyla that related to P cycling, Proteobacteria, Actinobacteria, Bacteroidetes, and Candidatus_Eremiobacteraeota were higher in organic soil; conversely, the three bacteria phyla (Acidobacteria, Verrucomicrobia, and Chloroflexi) and archaea taxa were more abundant in mineral soil. Therefore, we concluded that the distribution of genes and microbial taxa involved in soil P cycling differed among soil depths, providing a depth-resolved scale insight into the underlying mechanisms of P cycling by soil microorganisms in subtropical forests.